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Subject[PATCH 4.15 023/146] drm/radeon: Fix deadlock on runtime suspend
Date
4.15-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Lukas Wunner <lukas@wunner.de>

commit 15734feff2bdac24aa3266c437cffa42851990e3 upstream.

radeon's ->runtime_suspend hook calls drm_kms_helper_poll_disable(),
which waits for the output poll worker to finish if it's running.

The output poll worker meanwhile calls pm_runtime_get_sync() in
radeon's ->detect hooks, which waits for the ongoing suspend to finish,
causing a deadlock.

Fix by not acquiring a runtime PM ref if the ->detect hooks are called
in the output poll worker's context. This is safe because the poll
worker is only enabled while runtime active and we know that
->runtime_suspend waits for it to finish.

Stack trace for posterity:

INFO: task kworker/0:3:31847 blocked for more than 120 seconds
Workqueue: events output_poll_execute [drm_kms_helper]
Call Trace:
schedule+0x3c/0x90
rpm_resume+0x1e2/0x690
__pm_runtime_resume+0x3f/0x60
radeon_lvds_detect+0x39/0xf0 [radeon]
output_poll_execute+0xda/0x1e0 [drm_kms_helper]
process_one_work+0x14b/0x440
worker_thread+0x48/0x4a0

INFO: task kworker/2:0:10493 blocked for more than 120 seconds.
Workqueue: pm pm_runtime_work
Call Trace:
schedule+0x3c/0x90
schedule_timeout+0x1b3/0x240
wait_for_common+0xc2/0x180
wait_for_completion+0x1d/0x20
flush_work+0xfc/0x1a0
__cancel_work_timer+0xa5/0x1d0
cancel_delayed_work_sync+0x13/0x20
drm_kms_helper_poll_disable+0x1f/0x30 [drm_kms_helper]
radeon_pmops_runtime_suspend+0x3d/0xa0 [radeon]
pci_pm_runtime_suspend+0x61/0x1a0
vga_switcheroo_runtime_suspend+0x21/0x70
__rpm_callback+0x32/0x70
rpm_callback+0x24/0x80
rpm_suspend+0x12b/0x640
pm_runtime_work+0x6f/0xb0
process_one_work+0x14b/0x440
worker_thread+0x48/0x4a0

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=94147
Fixes: 10ebc0bc0934 ("drm/radeon: add runtime PM support (v2)")
Cc: stable@vger.kernel.org # v3.13+: 27d4ee03078a: workqueue: Allow retrieval of current task's work struct
Cc: stable@vger.kernel.org # v3.13+: 25c058ccaf2e: drm: Allow determining if current task is output poll worker
Cc: Ismo Toijala <ismo.toijala@gmail.com>
Cc: Alex Deucher <alexander.deucher@amd.com>
Cc: Dave Airlie <airlied@redhat.com>
Reviewed-by: Lyude Paul <lyude@redhat.com>
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Link: https://patchwork.freedesktop.org/patch/msgid/64ea02c44f91dda19bc563902b97bbc699040392.1518338789.git.lukas@wunner.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
drivers/gpu/drm/radeon/radeon_connectors.c | 74 +++++++++++++++++++----------
1 file changed, 49 insertions(+), 25 deletions(-)

--- a/drivers/gpu/drm/radeon/radeon_connectors.c
+++ b/drivers/gpu/drm/radeon/radeon_connectors.c
@@ -900,9 +900,11 @@ radeon_lvds_detect(struct drm_connector
enum drm_connector_status ret = connector_status_disconnected;
int r;

- r = pm_runtime_get_sync(connector->dev->dev);
- if (r < 0)
- return connector_status_disconnected;
+ if (!drm_kms_helper_is_poll_worker()) {
+ r = pm_runtime_get_sync(connector->dev->dev);
+ if (r < 0)
+ return connector_status_disconnected;
+ }

if (encoder) {
struct radeon_encoder *radeon_encoder = to_radeon_encoder(encoder);
@@ -925,8 +927,12 @@ radeon_lvds_detect(struct drm_connector
/* check acpi lid status ??? */

radeon_connector_update_scratch_regs(connector, ret);
- pm_runtime_mark_last_busy(connector->dev->dev);
- pm_runtime_put_autosuspend(connector->dev->dev);
+
+ if (!drm_kms_helper_is_poll_worker()) {
+ pm_runtime_mark_last_busy(connector->dev->dev);
+ pm_runtime_put_autosuspend(connector->dev->dev);
+ }
+
return ret;
}

@@ -1040,9 +1046,11 @@ radeon_vga_detect(struct drm_connector *
enum drm_connector_status ret = connector_status_disconnected;
int r;

- r = pm_runtime_get_sync(connector->dev->dev);
- if (r < 0)
- return connector_status_disconnected;
+ if (!drm_kms_helper_is_poll_worker()) {
+ r = pm_runtime_get_sync(connector->dev->dev);
+ if (r < 0)
+ return connector_status_disconnected;
+ }

encoder = radeon_best_single_encoder(connector);
if (!encoder)
@@ -1109,8 +1117,10 @@ radeon_vga_detect(struct drm_connector *
radeon_connector_update_scratch_regs(connector, ret);

out:
- pm_runtime_mark_last_busy(connector->dev->dev);
- pm_runtime_put_autosuspend(connector->dev->dev);
+ if (!drm_kms_helper_is_poll_worker()) {
+ pm_runtime_mark_last_busy(connector->dev->dev);
+ pm_runtime_put_autosuspend(connector->dev->dev);
+ }

return ret;
}
@@ -1174,9 +1184,11 @@ radeon_tv_detect(struct drm_connector *c
if (!radeon_connector->dac_load_detect)
return ret;

- r = pm_runtime_get_sync(connector->dev->dev);
- if (r < 0)
- return connector_status_disconnected;
+ if (!drm_kms_helper_is_poll_worker()) {
+ r = pm_runtime_get_sync(connector->dev->dev);
+ if (r < 0)
+ return connector_status_disconnected;
+ }

encoder = radeon_best_single_encoder(connector);
if (!encoder)
@@ -1188,8 +1200,12 @@ radeon_tv_detect(struct drm_connector *c
if (ret == connector_status_connected)
ret = radeon_connector_analog_encoder_conflict_solve(connector, encoder, ret, false);
radeon_connector_update_scratch_regs(connector, ret);
- pm_runtime_mark_last_busy(connector->dev->dev);
- pm_runtime_put_autosuspend(connector->dev->dev);
+
+ if (!drm_kms_helper_is_poll_worker()) {
+ pm_runtime_mark_last_busy(connector->dev->dev);
+ pm_runtime_put_autosuspend(connector->dev->dev);
+ }
+
return ret;
}

@@ -1252,9 +1268,11 @@ radeon_dvi_detect(struct drm_connector *
enum drm_connector_status ret = connector_status_disconnected;
bool dret = false, broken_edid = false;

- r = pm_runtime_get_sync(connector->dev->dev);
- if (r < 0)
- return connector_status_disconnected;
+ if (!drm_kms_helper_is_poll_worker()) {
+ r = pm_runtime_get_sync(connector->dev->dev);
+ if (r < 0)
+ return connector_status_disconnected;
+ }

if (radeon_connector->detected_hpd_without_ddc) {
force = true;
@@ -1437,8 +1455,10 @@ out:
}

exit:
- pm_runtime_mark_last_busy(connector->dev->dev);
- pm_runtime_put_autosuspend(connector->dev->dev);
+ if (!drm_kms_helper_is_poll_worker()) {
+ pm_runtime_mark_last_busy(connector->dev->dev);
+ pm_runtime_put_autosuspend(connector->dev->dev);
+ }

return ret;
}
@@ -1689,9 +1709,11 @@ radeon_dp_detect(struct drm_connector *c
if (radeon_dig_connector->is_mst)
return connector_status_disconnected;

- r = pm_runtime_get_sync(connector->dev->dev);
- if (r < 0)
- return connector_status_disconnected;
+ if (!drm_kms_helper_is_poll_worker()) {
+ r = pm_runtime_get_sync(connector->dev->dev);
+ if (r < 0)
+ return connector_status_disconnected;
+ }

if (!force && radeon_check_hpd_status_unchanged(connector)) {
ret = connector->status;
@@ -1778,8 +1800,10 @@ radeon_dp_detect(struct drm_connector *c
}

out:
- pm_runtime_mark_last_busy(connector->dev->dev);
- pm_runtime_put_autosuspend(connector->dev->dev);
+ if (!drm_kms_helper_is_poll_worker()) {
+ pm_runtime_mark_last_busy(connector->dev->dev);
+ pm_runtime_put_autosuspend(connector->dev->dev);
+ }

return ret;
}

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